Irradiation experiments of CCl3F were carried out with60Co γ-rays using the irradiation facility of the flow system. In the system, CCl3F was irradiated at 5.7 kGy/h (5.7×105 rad/h) and -30°C. The decomposition behavior of CCl3F and the influence of impurities in the circulating gas on the decomposition were examined. The result was compared with that of ampoule scale. The decomposition yield of CCl3F and the yields of radiolytic products ( fluorocarbons) increased in proportion to the absorbed dose. The decomposition yield per Mrad of CCl3F was 0.0246 mol%/Mrad (G=2.9) . This value was equal to 1.8 times that of the ampoule scale. The marked influence of impurities (air, CH4, I2) was recognized for the yields of halogen ions.
In order to study the metabolic fate of etofenamate [I], an anti-inflammatory agent, the14C-labelled compound of I was synthesized. The14C-labelled compound of flufenamic acid [II], the major metabolite of I, was also synthesized to compare the metabolic fate of I with that of II. N-Benzyl-N- [α, α, α-trifluoro-m-tolyl] [carboxyl-14C] anthranilic acid [IV-14C] was prepared by the reaction of the Grignard reagent prepared from N-benzyl-2-bromo-3'-trifluoromethyl-diphenylamine [III] with [14C] carbon dioxide. After condensation of IV-14C with 2-benzyloxy-2'-chlorodiethylether, hydrogenolysis of the resulting ester [V-14C] gave [carboxyl-14C] etofenamate [I-14C] . IV-14C was similarly hydrogenolized to give [carboxyl-14C] flufenamic acid [II-14C] . The overall radiochemical yields of I-14C and II-14C from barium [14C] carbonate were 56 and 50%, respectively.
The dispersal rates of radioisotopes under normal chemical operations were determined with a view to obtaining a fundamental information, which will be applicable to reasonable design of laboratory and safety handling of radioactive materials. A total of 16 samples was selected from widely used radioisotopes. The dispersal rate is defined as the ratio of radioactivity released from the vessel in a unit time to whole radioactivity. The results showed that the dispersal rates varied widely according to nuclide and chemical form. The higher values were obtained from3H (amino acid mixture), 14C (amino acid mixture), 35S (cysteine) and 75Se (selenomethionine) with average levels ranging from 4×10-5/h to 7×10-4/h. The values of radioiodines such as125I (sodium iodide), 125I (triiodo-thyronine) and131I (sodium iodide) ranged between 4×10-6/h and 2×10-5/h. The lower values were observed for32P (phosphoric acid), 35S (sodium sulfate), most nuclides of the metallic elements, etc., in which the values lied in less than the order of 10-7/h. On the basis of these experimental evidences, the relationship between the dispersal rates and the natures of nuclides and of chemical forms is discussed.